They came on a 12V 842HR that I bought as a back-up radio for my 56 Dodge. The knobs fit correctly but they are not 56 Dodge knobs although the radio is marked as having come from a 56 Dodge. IF we can figure out what the knobs are for, I will likely put them up for sale for a reasonable price.

The 842HR does not have the Electro-Touch Tuning of the 910HR but it does have 5 preset buttons and a sixth "OFF" button that allows the radio to be shut off without touching the volume knob. (So I am told).